Apparatus for printing code marks from a fluid medium



May 5, 1969 Q P, COPPlNG ET AL v v 3,442,208

APPARATUS FOR `PRINTING CODE MARKS FROM A FLUID MEDIUM ATTQRNEY f May 6, 1969 G. F. coPPlNG ET AL l Y' v3,442,208` APPARATUS FOR PRINTING CODE MARKS FROM A FLUID MEDIUM Filed Aug.` s, 196e sheet 2 of i1 INVENTOZJ ,Air-Talamm..

May 5, 1969 G. P. coPPlNG ET AL. I 3,442,208

APPARATUS RoR PRINTING com: MARKS FROM A FLUID MEDIUM Filed Aug. s. 1966 sheet 3 of 4 lNvENToz s ATTozNeY May '6, 1969 G.'P. CPPING ET AL. 3,442,208 Y APPARATUS FCR PRINTING CODE MARKS FROM A FLUID MEDIUM Filed Aug. e. 1966 sheet 4 of 4 F/G. Z

' fanfxfrf? @Wwf Mund/1 W# ffy/Fabro INVENTQIZS vA1 vom EY United States Patent O U.S. Cl. 101--318 6 Claims ABSTRACT OF THE DISCLOSURE Apparatus for printing code marks on letters comprises a first container for printing ink and from which a stream of printing ink is allowed to flow down a guide surface to a second container from which the ink is pumped back to the first container. Projecting through the guide surface and into the stream is a series of printing pins. Electromagnets are fitted to the pins to move a selection of the pins so that the heads thereof Contact the letter to be marked.

This invenion relates to printing methods and apparatus and has particular, but not exclusive, reference to methods of, and apparatus for, printing one or more code marks on a surface, for example, the surface of a letter or other postal item. The code marking is a translation of part of the address on the item and is used in the control of automatic machinery through which the item passes during sorting and/or other processes.

In the code marking of postal items, marking must be effected very rapidly, but if an ink is used which incorporates an extremely volatile carrier in an attempt to speed up drying, it is found that the ink congeals and dries on the code printing mechanism and in ink reservoirs feeding the mechanism. If phosphorescent marking is required, it has been necessary to coat a flexible tape with the phosphorescent material, and to transfer the latter from the tape to the surface to be marked by heated code pins or other printing devices. This method is not entirely satisfactory. The tape is expensive and only a small fraction of its surface is used, the remainder being wasted. Constant cleaning of the pins is necessary and it is not easy to heat the pins.

According to the present invention a method of imprinting a series of code marks on a surface includes the steps of maintaining a flow of a liquid printing medium over at least the printing surfaces of each of a series of code mark printing members, operating a combination of the printing members to move the printing surfaces thereof clear of the flow of liquid printing medium and into contact with the surface and then returning each member of the operated combination to its initial position.

The printing medium may be a substance which is a solid at normal room temperatures, and for use with such a medium the present invention provides a method of imprinting a series of code marks on a surface including the steps of maintaining a normally solid printing medium in a molten state, allowing a film of the molten medium to flow continuously over the printing surfaces of each of a series of hot code mark printing members. operating a combination of the printing members to bring the printing surfaces thereof clear of the film and into contact with the surface on which the code marks are to be imprinted, and then returning each member of the operated combination to its initial position.

The combinaion may comprise one, some or all of the printing members.

The temperature of the hot printing members must be at least equal to the melting point of the solid printing medium but preferably it is equal to the temperature of the molten printing medium.

Operation of the printing members may cause them to advance towards the surface and, after imprinting code marks on the latter, to withdraw through the film before returning to the initial position.

Apparatus for imprinting a mark on a surface comprises at least one printing member having a printing surface, means for passing a flow of liquid printing medium over the printing surface, and means for moving the printing surface of the printing member clear of the fiow of liquid printing medium and into contact with the surface and subsequently returning the member to its initial position.

ere the printing medium is a substance which is solid at normal temperatures the present invention also provides apparatus for imprinting a series of code marks on a surface comprising a first container for holding molten printing medium, a second container for holding molten printing medium, at least two flow paths for the molten medium between the first and the second container, a series of printing members having each of their printing surfaces located in a one flow path, a second return circuit fiow path for returning molten medium from the second container to the first container, and heating means for both containers, the flow paths, and the printing members.

The first container may be positioned at a higher level than, the second container, and the printing members at an intermediate level. Molten medium can then flow under gravity from the rst container to the second container via a first flow path. In this case, the return circuit fiow path includes a pump for lifting the molten material from the second container to the first container.

In the embodiments in which the printing medium is a substance which is a solid at normal temperatures the heating means may comprise tubes located inside the containers or around or within the walls of the containers. These tubes are preferably formed of copper, and may be fluid-filled, or alternatively, electrical heating elements may be threaded through them. When electrical heating elements are used extra care is necessary to avoid the risk of overheating, particularly when the medium is in its solid state and no convection currents can flow in the medium.

The printing members may be in the form of pins housed in a support structure comprising guide tubes located in the first container and so heated thereby. The pins are slidably mounted in the guide tubes and have their end faces positioned in a flow path. The first container may have apertures in `its wall through which the molten material flows.

The printing pins may be disposed in a single row or in several rows arranged one above the other and, in the latter case, corresponding pins in different rows may be in line with one another.

By way of eXamp-le only, printing methods and apparatus embodying the invention will now be described in greater detail with reference to the accompanying drawings of which:

FIG. 1 is a side view partly in section showing a first embodiment in diagrammatic form only,

FIG. 2 is a side view partly in section showing a second embodiment in diagrammatic form only,

FIGS. 3 and 4 are views on an enlarged scale of alternative forms of a detail of the first and second embodiment,

FIG. 5 is a section along the line V-V of FIG. 6, of a third embodiment,

FIG. 6 is a section along the line VI-VI of FIG. 5, and

FIG. 7 is a section along the line VII- VII of FIG. 6.

The embodiment shown in FIG. l is suitable for printing code marks on receiving surfaces for example letters and similar postal items and comprises a container or tank 1 for holding molten printing medium. The tank 1 is 'vented at 2 to atmosphere, and is mounted on a base 3 beneath which is a reservoir container or tank 4 in communication with tank 1 via an overow pipe 5 in the tank and via a pumping chamber 6 having nonreturn exit and entrance valves 7 and 8. Along one wall 9 of the tank 1 is a support structure comprising a guide block 10 supporting a number of horizontal guide tubes 11 which extend from the block 10 through the tank 1 as shown. Immediately above each guide tube 11 both the -block 10 and the wall 9 are apertured as indicated at 12. The block 10 extends beyond the lower edge of wall 9 and, through an elongated aperture 13 in the base 3, into the reservoir tank 4. The lower edge of block 10 is bevelled as indicated at 14.

A calorier coil 15- has a part of its length located inside tank 1 and a part inside reservoir tank 4. The coil is joined via flow pipes 16 to a tank 17 containing an electric immersion heater 18. If necessary, a circulating pump indicated by block 19 can be included and the tank 17 is fitted with the known expansion pipe 20 and make-up tank 21.

Each guide tube 11 contains a printing pin 22 which when at rest projects slightly from the left-hand end (as seen in FIG. 1) of the guide tube and to a greater extent from the right-hand end, Each pin carries a collar 23- ixed to it and each is connected to its own carn follower lever 24. The pin passes loosely through the lever but resilient connection between a pin 22 and its lever 24 is maintained by a light helical spring 25 which encircles the pin over part of the length of the latter and is positioned between the collar 23 and a washer 26 on the pin adjacent the lever. Screwed over the right-hand end (as viewed in FIG. 1) of the pin is a nut 27 rotation of which varies the relative positions of the pin and lever. Each lever is biassed into contact with an individual operating cam 2S by a spring 29. The cams are rotated by driving mechanism not shown but whose function will be dealt with later.

The pumping chamber 6 is joined by a tube 30, containing a U-bend 31, to a reciprocating pump shown diagrammatically in FIG. 1 as comprising a piston-cylinder assembly 32, the piston 33 being attached to a lever 34 driven by a rotatable cam 35. The U-bend contains mercury indicated at 36.

The base 3 extends forwardly of the block 10 and provides a platform for the reception of letters and similar postal items to ybe marked. The item is fed (by a mechanism .not shown) to a position in between a movable platen 37 with the area of the item to be marked aligned with the printing pins 22 and a fixed guide plate 38 apertured to permit printing movement of the pins 22 as will be described later.

The printing medium used consists of particles of a solid phosphorescent material dispersed in a carrier. The carrier should be a substance which is solid at normal room temperatures and has a melting point not far above those temperatures, for example the melting point may lie in the range 65 C.-80 C. The carrier should also set solid within a short period for example, 100` milliseconds -only, without super-cooling at temperatures below its melting point. It should also adhere satisfactorily to the paper commonly used for envelopes, postcards, etc., and must be stable, non-toxic and free from unpleasant smells. It must, of course, be compatible with the solid phosphorescent material used so that particles of the latter remain dispersed throughout the medium without forming agglomerates, or reacting chemically with the carrier, and so that the luminescence of the phosphor is unimpaired. The carrier might be transparent to ultra-violet and visible light.

A suitable carrier is a 5% solution of polystyrene or gum dammer in diphenyl. This material melts at approximately 70 C. and when melted can be loaded with fine particles of phosphor powder which may be kept in suspension and uniformly dispersed by suitable agitation. Suitable proportions are from four to six parts by weight of solid carrier to one part by weight of phosphor pOW- der. As will be described later, the medium is used at a temperature of from 78 to 90 C. so that critical control of temperature is not required. In general, the higher the temperature at which the medium is used the longer the time taken to solidify.

The phosphor may be one of those described in British patent specification No. 870,504, for example, a cyanuric acid-formaldehyde resin activated by carbazole sulphonic acid'. The printing medium is prepared by melting a quantity of the carrier adding th-e requisite weight of phosphor thoroughly mixing in to ensure even dispersion and then allowing the mixture to cool. The resultant solid is broken into fragments for use as will now be described.

Before the apparatus is ready for use the tank 1 is loaded with fragments of solid printing medium and hot water is circulated through the calorier coil 15. Cam 35 is also set in motion but at this stage motion of the piston 33 has no effect because the pumping chamber 6 is empty and the medium is still solid.

In due course, the solid medium melts completely and commences to flow through the apertures 12, along a flo-w path down the face of the guide block 10 and into the reservoir tank 4. The printing medium is maintained in a molten state in the reservoir tank 4 by that part of the calorifier coil located therein. Reciprocation of piston 33 causes pressure fluctuations in the pumping chamber 6 and molten medium is drawn into the chamber via the non-return valve 8 and pumped up into the tank 1 via the non-return valve 7 and an aperture 39 in the base 3. The function of the mercury 36 is to limit movement of the liquid medium and vapour to that part of the tube 30 Within the heated reservoir tank 4. Thus neither the liquid medium nor the vapour comes into contact with nonheated surfaces and blockage of the pump which would otherwise occur due to solidiication of the liquid or vapour does not happen. The mercury is, of course, impervious to both the molten medium and its vapour. The rate of pumping is such that molten medium enters the tank 1 with a velocity suicient to create in the molten medium already in that tank a degree of turbulence, thereby assisting the maintenance of the phosphor in suspension.

The flow of molten medium over the face of the guide block 10 washes the printing 'faces of the printing pins 22, the positioning of those printing faces in the flow being such that they almost break through the surface of the flow. However, a thin film of molten medium is maintained over the end faces of the pins 22 as shown in FIG. 3. The rest position of a pin thus determines the amount of molten medium transferred to the surface of a postal item to be printed, and this avoids the need to maintain a thin film over the entire surface of the block. The limited iiow necessary to obtain such a thin film would be difficult to maintain since apertures 12 would need to be of small diameter and would tend to clog. Thearrangement described permits a larger and hence thicker flow from larger orifices which is more easily maintained, without resulting in the transfer of too much medium to the item.

It will be appreciated that the location of the pins is such that they too are maintained substantially at the temperature of the molten medium, and none of the latter adheres to the pins as it iiows over them.

The apparatus is now ready to print and postal items to be printed are fed sequentially to a position in front of the printing pins. When a letter reaches that position, the platen 37 is moved forward to hold the item firmly against the fixed guide plate 38. A requisite combination of the cams 28 is then driven through a single revolution and this causes a linear motion of the printing pins associated with the driven cams. When a pin has been moved into contact with the surface to be imprinted, further movement of its lever 24 in the same direction compresses its spring 25, so that the pin does not damage the surface. On forward movement the pins break through the fiow of molten medium but carry with them a thin film of the latter on the printing face of each pin. The thin film is transferred to the surface of the postal item where it solidifies rapidly and the pins are withdrawn to positions to the rear of the initial positions and then move forwardly into the latter. In FIG. 3, the initial position is indicated at A, the printing position at B and the most rearward position at C. During the movement from position C to position A the printing faces of the pins are thoroughly wetted by the comparatively thick 4film of molten medium flowing down the face of the guide block and this cleans any deposit from the printing faces of the pins and also facilitates the maintenance of the thinner film when the pins reach position A.

The means feeding postal items and holding themin position and for selecting the requisite combination of pins do not form part of the present invention and can take any suitable form. For example the feeding and holding means described in British patent specification No. 939,233 might be used in which case the apparatus described above will be located in the coding position.

The second embodiment now to be described with reference to FIG. 2 is generally similar to the first embodiment described above with reference to FIG. 1 and the same reference numbers have been used in FIG. 2 aS in FIG. 1 for similar parts.

In the second embodiment containers for the molten printing medium are immersed in a liquid bath. A main tank 1 and reservoir tank 4 are immersed in a container 39 of water heated by an electric immersion heater 40. The tank .1 is connected with the tank 4 via an overiiow pipe 5 and a pumping chamber 6 with non-return outlet and inlet valves 7, 8. Also connected to the tank 1 is a hopper 41 partly submerged in the water in container 39.

Secured internally of the container 39 to the front wall 42 thereof is a manifold 43 joined to the tank 4 by a iiow tube 44 and vented to atmosphere by tube 45. Also mounted in the front wall 42 and directly 'beneath the manifold is a collecting trough 46 joined to the reservoir tank 4 by a iiow tube 47.

Pressure fluctuations are applied to the pumping chamber 6, from a piston-cylinder arrangement 32 as before, via the tube 30 and U-bend 31 containing mercury 36.

The apertures 12 are positioned as shown in that part of the front wall 42 bounding the manifold 43, and, from the apertures, guide tubes 11 extend rearwardly through the container 39. From FIG. 4 it will be seen that the ends of the tubes 11 located in the apertures 12l are notched as at 48 to permit flow of molten printing medium through the apertures. Printing pins 22 slidably mounted in the guide tubes 11 are positioned in the manner described above and are joined to individual cam follower levers 24 pivoted at 49 and in contact with individual cams 28. The embodiment of FIG. 2 employs a somewhat different mechanism for controlling movement of the printing pins 22. Each pin has a latching extension S0 slidable in a member 51 and associated with a latch 52 connected to the armature 53 of a solenoid 54. Ihe arrangement is such that rotation of the cam 28 of a particular printing pin produces linear movement of the pin only if the latch 52 is disengaged from the latching extension 50. Unless the` latch 52 is disengaged,

spring 25 is compressed by the cam follower lever but there is no movement of the pin.

The reservoir tank 4 has a drain tube 55 fitted with a stop-cock 56.

The forms of orifice shown in FIGS. 3 and 4 are alternatives, either of which may be used in FIG. 1 or FIG. 2. That shown in FIG. 4 has the advantage that the pin movement tends to keep the orifice clear of blockage by particles of medium.

Before use, fragments of solid printing medium are fed into hopper 41, the container 39 being filled with water which has been brought to the required temperature by the heater 40. The solid medium melts and iiows into tank 1. In due course the tank 1 is filled and molten medium flows into the manifold 43 via the flow tube 44 to form a small accumulation in the lower part of the manifold 43. When the level of medium inside the manifold 43 reaches the apertures 12, the medium iiows out through the apertures and down a flow path along the outer surface of the wall 42 and is collected by the trough 46 and returned to the reservoir tank via the flow tube 47, and is pumped back to tank 1 as described above.

A letter 57 or similar postal item to be printed is fed by means not shown to the position indicated in full lines and is then moved towards the fixed guide plate 3S by the movable platen 37. With the item held firmly, a requisite combination of latches 52 is disengaged from the associated latching extensions 50 and the appropriate pins move towards the item and then away from it in the manner described above. After printing the item is moved away and is replacediby a succeeding item.

In the third embodiment two rows of printing pins are mounted one above the other, and the printing medium flows along a fiow path rstly over one row of pins, is collected, and subsequently over a second row of pins.

The printing medium is held in the upper containers 1A and 1B, and in the lower reservoir 4. The printing pins 22A and 22B are cranked as shown so that the `rear (righthand side as shown in FIG. 5) guides 11A and 11B are vertically higher `than the front guides 11C and 11D. The printing medium is heated by electrical cartridge heaters inserted `into holes 60 in the base of containers 1A and 1B, and the reservoir 4; the heaters are thermostatically controlled to maintain the printing medium in the molten state. The medium is raised from the reservoir 4 through the tube 61, Vby the impeller 62, which is driven by the motor 63, through the concentric shaft 64. This impeller also assists in the mixing of the printing medium. The tube 61 passes through middle container 1B and trough 66, being sealed into the base of container 1A. The tube 61 is surrounded by an annular aperture 71 in the base of trough 66, but is sealed into the base of middle container 1B.

From the upper container 1A the medium fiows through a series of orifices 12 and along a fioiw path over the printing faces of the upper printing pins 22A. The orifices 12 are of the type described with reference to FIG. 4. The level of printing medium is maintained in the upper container 1A at a level intermediate the orifices 12 and the rear guides 11A. The combined rate of outflow of medium through the orifices 12 and an outlet tube 65 in the floor of the container 1A depends upon their size and the head of medium in the container. The impeller 62 maintains a constant rate of input of medium, so chosen that, for given sizes of orifices 12 and outlet tube 65, equilibrium is reached when the medium in the container is at the desired level. This ensures that medium cannot reach the rear guides where it might form a solid sleeve on the pin shafts behind the guides 11A by being cooled below its freezing point on the relatively cooler part of the shaft, and hence impede future movements of the printing pin.

Printing medium which overfiows from the upper container runs into a collecting trough 66 where it mixes with that which has passed through the orifices 12 and runs down the lower portion of the container into the collecting trough. As seen in FIG. 6 this trough slopes towards the impeller tube 61, and medium runs down this trough and through the annular aperture 71 into the middle container 1B.

The middle container 1B, containing the lower row of printing pins, is of exactly similar `form to the upper container 1A, and the flow of the printing medium follows an exactly similar path. When the medium overows and runs off the bottom of the lower container 1B, it runs into the lower reservoir 4, from which it is recycled by impeller 62 into the upper reservoir 1A.

The containers 1A, 1B and reservoir 4 are mounted on a plate 67 which provides a rigid support to maintain them in their correct relative positions. This plate has a rectangular portion 68 cut away to allow adequate space for fluid to iiow down the front faces of the containers 1A and 1B and, over this rectangular hole, a masking plate 69 is fixed. This plate is apertured as at 70A, 70B, and letters are clamped against the plate for printing as described previously.

The printing pins can be actuated by either of the methods described with reference to FIG. 1 or FIG. 2, or by any other suitable method.

It will be appreciated that the embodiments described above are given by way of example only because many of the components can be replaced by equivalent components of different form. Other forms of circulating pump could be used, for example, diaphragm pumps, the operative parts being heated so as to prevent blockage as de scribed above. The linear motion of the printing pins may take a form other than that described above, for example the position C may be omitted. In addition, more rows of printing pins may be used than the single row or double rows described above. If two or more rows are used, the pins of the rows can be directly beneath one another and can be fed from orifices positioned directly above the pins of the .topmost row. The flow of molten medium is such that starvation of the lower row pins does not occur.

Further, the appaartus can be used to mark surfaces other than those of postal items and can be used with uorescent or other marking medium which requires to be kept in a molten condition.

We claim:

1. Printing apparatus for imprinting at least one mark n a receiving surface comprising in combination at least one printing pin, each printing pin having a printing face, a support structure for each printing pin enabling the latter to be reciprocated longitudinally, means for reciprocating each pin longitudinally, a container for holding a printing medium, a reservoir for holding printing medium, a printing medium flow path from the container to the reservoir and back, said support structure supporting each printing pin with its printing face located in the ow path from the container to the reservoir, at least part of said support structure being housed in said container which has a wall through which each said printing pin extends, and support means for supporting the said receiving surface adjacent the printing pin so that the surface is substantially normal to the reciprocation of the pin.

2. Printing apparatus as claimed in claim 1 and further comprising a plurality of printing pins each of which is cranked and has one portion having said printing face disposed in the container, and a second portion mounted in said support structure.

3. Printing apparatus as claimed in claim 2 and further comprising guide means for the said one portions of the printing pins, and contoured surfaces on said guide means to permit egress of printing medium from said container.

4. Printing apparatus as claimed in claim 3 and further comprising an outlet from the container of a size adapted to maintain the level of printing medium in the container at a level between said contoured surfaces and said second portions of said printing pins.

5. Printing apparatus as claimed in claim 1 and further comprising an intermediate container spaced from and positioned below said irst named container and spaced vertically above said reservoir.

6. Printing apparatus as claimed in claim 5 in which each of said containers except the lowermost is mounted above a trough, said trough being adapted and arranged to collect printing medium egressing from the container and to direct printing medium to the container positioned immediately below said trough.

References Cited UNITED STATES PATENTS 1,010,594 12/1911 Cowles 118-243 X 2,288,015 6/1942 Mumma lOl-327 2,488,685 11/ 1949 Riddle 118-243 X 3,277,566 10/1966 Christensen 118-300 X ROBERT E. PULFREY, Primary Examiner.

FRED A. WINANS, Assistant Examiner.

U.S. Cl. X.R.

lOl-327; 118-211, 243 

